The usual pair of spectacles, as this term has been defined above, comprises a frame which may have a bridgepiece interconnecting a pair of window-forming portions which can be provided with respective lenses, with a respective temple being pivotally connected to each of these portions and formed with an earpiece.
When the spectacles are worn, the frame is supported on the nose of the wearer by the bridgepiece, the lenses are located in front of the eyes, and the temples extend rearwardly along the sides of the head and may engage, e.g. with earpieces, behind the ears of the wearer.
Spectacles have been provided for a wide variety of purposes only some of which need be alluded to here. For example, they may be provided as ordinary eyeglasses with corrective lenses or lenses intended to assist in normal vision, either fabricated specially for the user or to provide magnification or some other special effect.
Sunglasses, for example, may be used as filters or attenuators to protect the eyes from the sun, while stereoscopic glasses may be used to provide three-dimensional illusions in viewing three-dimensional displays in which two distinct images are created by polarized light or color effects.
Colored-lens glasses may also be used simply as novelty items without sunlight filtering effects.
Spectacles may also be used to protect the eyes against vapors, the spattering of liquids and flying particulates.
For conventional frames, synthetic resin materials may be used or other materials such as wire and metals can be employed in whole or in part. Disposable or single-use spectacles, e.g. as sunglasses or for viewing three-dimensional motion pictures may be distributed widely at low cost and may utilize materials such as cardboard or paperboard.
In recent years, a compact construction has been desired. In the standard mode of use, the temples of a pair of spectacles are permanently hinged at the outer ends of the frame to allow the temples to be swung inwardly and enable the folded pair of glasses to be inserted into a standard sleeve, into a pocket or otherwise stored. Sometimes a hinge or flexible connection is provided at the bridge piece to enable the spectacles to be folded into a somewhat more compact configuration.
While these systems have proved to be relatively compact, they invariably are somewhat bulky and it is desirable in some cases to provide an extremely flat construction.